The present invention relates to a method and apparatus for forming a lumber stack, and more particularly to a novel method and apparatus for forming a lumber stack and placing sticks between adjacent tiers or courses in a stack being formed.
In the stacking of lumber, it is conventional to place sticks between adjacent courses during laying of the courses so that the courses are vertically spaced-apart according to the thickness of the sticks. Whether mechanically or manually placed on a course prior to the laying of the next course, the sticks are generally positioned tranversely to the longitudinal dimension of the stack. The actual number of sticks placed depends upon the length of the stack, the primary consideration being to space adjacent courses from one another so that adequate air circulation may be obtained during drying of the stack in a kiln.
There are several problems present in known lumber stacking apparatus which arise out of the difficulty of accurately placing or depositing sticks. Sticks are generally dimensioned one inch by two inches for a given length, with the two inch dimension being deposited to face adjacent courses. It is necessary that stick placement not inadvertently result in some of the sticks having the shorter or one inch dimension facing the adjacent courses. This is because the lumber on a course must repose generally horizontally and in parallel relationship with adjacent courses or warpage during drying will occur. Unfortunately, it has been difficult to develop apparatus for placing sticks which will ensure that the sticks do not become improperly oriented during placement on a course.
Additionally, several known apparatus for stacking lumber and placing sticks require that the sticks be dropped from a given elevation onto a course disposed therebeneath. During dropping, the sticks may become skewed relative to the lengthwise dimension of the stack as well as inadvertently bounce so that their width faces vertically. Thus, it is a considerable problem to provide a method, other than manual stick placement, which will ensure reliable and accurate placement of sticks. Of course, manual stick placement is extremely wearisome as well as time consuming and therefore uneconomical.
Another problem with known apparatus for placing sticks resides in the fact that it has been difficult to provide a design which will enable vertical dropping of only a selected stick from a stick containing bin. Stated differently, complicated mechanisms must be provided in order to retain sticks and selectively drop only a single stick at a preselected location on a course. Certainly, if more than one stick is dropped at a preselected location on a course, wastage of materials will result as well as the possibility of stacking sticks which may cause uneven laying of a course on a stack.
Still another problem present with prior art apparatus for stacking lumber and placing sticks resides in the lack of separating adjacent pieces of lumber in each course so that air flow will be permitted to travel vertically upwardly between the courses in a kiln to ensure adequate drying of the lumber. In this regard, it is to be noted that separation of lumber in the courses must not be such that opposite side boundaries of the stack do not define substantially vertical planes. The requirement for vertical planes is based on the fact that even sweeping of air during drying over the stack would be adversely effected if lumber adjacent the vertical sides of the stack were not stacked evenly.
Accordingly, it is a general object of the present invention to provide an apparatus for forming a lumber stack by laying successive courses and providing sticks between adjacent courses which includes a placing means operable for selectively depositing sticks generally transversely to the lengthwise dimension of a course by first receiving a stick, directing it through a predetermined angular displacement and then releasing same to the course at laterally spaced locations thereon.
More particularly, it is an object of the present invention to provide an apparatus for placing sticks in which the placing means includes a driven rotary feed means having a plurality of wheel sets disposed above a stacking station which receives a lumber course. Each wheel set is disposed beneath a stick-containing bin and includes a pair of opposed spaced-apart concentrically mounted wheels, each wheel being rotatable and provided with a plurality of stick-receiving means aligned with corresponding stick-receiving means on an associated opposed wheel. Upon rotation of the wheels, the stick-receiving means is movable through the predetermined angular displacement for receiving a stick from the bin with the stick's longitudinal axis being generally positioned parallel to the axis of rotation. By providing such a construction, it is possible to charge or load the wheel sets continuously with sticks and periodically release them onto spaced-apart locations on a receiving course.
Still another object of the present invention is to provide wheel sets, as described above, in which the stick receiving means are each defined by a plurality of notches or recesses formed adjacent the outer periphery of each wheel. The recesses are dimensioned for receiving and holding a stick so that it may be directed through the predetermined angular displacement from a position beneath a bin to a position for dropping the stick. Additionally, with a plurality of recesses being provided, each wheel set may continuously hold and direct through the predetermined angular displacement a plurality of sticks.
Yet another object of the present invention is to provide an apparatus, as described above, further including detaining means provided adjacent one wheel of each wheel set selectively operable for engaging one end of a released stick and momentarily maintaining it above a course prior to complete release of the stick. Stated differently, it is contemplated that upon movement of a stick through the predetermined angular displacement, one end of the stick will be dropped onto the course but the other end, after being released from the opposed wheel, will be momentarily prevented from dropping onto the course. The advantage in detaining one end of a stick resides in the fact that bouncing of a stick may be substantially prevented which ensures that a stick will not become skewed relative to the lengthwise dimension of a course or tipped up on its edge. By permitting one end to contact the course first, and then permitting the other end to drop, a more recise, controlled depositing of a stick is obtained.
Still a further object of the present invention is to a provide an apparatus, in which an overall embodiment contemplates the provision of a conveying means operable for transferring a course to be stacked to a first station and a positioning means operable for selectively elevating the course, horizontally as a unit, and then shifting it into position above a stacking station prior to operation of the above-described placing means. Further elaborating, the present invention contemplates that the positioning means, which includes a carriage means operable for shifting in the direction of conveyance, is additionally operable for elevating the course and shifting it directly beneath the placing means. It is necessary to elevate the course in order to pick it off the riding surface of the conveying means and separate it from upstream lumber. Additionally, it is necessary to shift the elevated course to a position as close as possible beneath the wheel sets so that each stick, as it is dropped, need fall only a minimal amount.
These and additional objects and advantages of the present invention will be more clearly understood from a consideration of the following drawings taken together with a detailed description of the preferred embodiment.